Re: gEDA-user: Adding Auto-thermals Was:Re: Thanks a million, and few small questions for a new user

[DJ Delorie <dj@xxxxxxxxxxx>]

> Did you mean auto-thermal and THERMAL flag, or do each via and pin
> have a VIA flag which indicates whether it needs a thermal?

Each pin/via has a set of flags, one for each layer, that says if it
should have a thermal, and what type.

In addition, apparently, each rat line has a flag that says if it can
be implemented as a thermal to a polygon on some layer.

> Also, you mention a pin can be within a surface polygon but isolated
> from it. What is a surface polygon (as apposed to an ordinary
> polygon)?

Consider a ground plane on the back of a two-layer board.  It's a big
rectangle.  However, traces on the back may "cut out" part of the
rectangle to leave a bare area.  You cannot use a thermal to connect
to the ground plane here, but if you just look at the big rectangle
you'd think you could.

This is less of an issue if the ground plane is on an internal layer,
only because there's less chance of there being traces there.  Still
you have to check no matter which layer it's on.


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